Production of phosphoric acid catalyst



Patented Aug. 25, 1953 PRODUCTION OF PHOSPHORIC ACID CATALYST Julian M.Mavity, Hinsdal versal Oil Products Co corporation of Delaware e, 111.,assignor to Unimpany, Chicago; 111., a

No Drawing. Application October 2, 1950, Serial No. 188,061

1 This application is a continuation-in-part of my copending applicationSerial Number 122,- 596, filed October 20, 1949, and now abandoned. Thisinvention relates to the production of solid catalytic material usefulin accelerating various types of reactions among organic compounds.

In a more specific sense, the invention is concerned with the productionof a particular type of solid catalyst which has special properties bothin regard to its activity in accelerating and directing olefinpolymerization reactions, its stability in service, and in itsrelatively low corro sive properties when employed in ordinarycommercial apparatus comprising various types of steel. An object ofthis invention is a method of producing a hydrocarbon conversioncatalyst which has a high resistance to crushing during use.

Another object of this invention is a highly active catalyst suitablefor use in the polymerization of olefinic hydrocarbons and in otherhydrocarbon conversion reactions involving olefins.

One specific embodiment of this invention retin.

Another embodiment of this invention relates to a process for improvingthe structural strength of a calcined composite of an acid of phosphorusand a siliceous solid which comprises treating said composite with ahydrolyzable salt of a metal selected from the group consisting oftitanium, zirconium, and tin.

A further embodiment of this invention relates to a process forimproving the structural strength and activity of a calcined compositeof a polyphosphoric acid and a siliceous adsorbent which comprisestreating said composite with a hydrolyzable salt of titanium.

A still further embodiment of this invention relates to a process forimprovin the structural strength and activity of a calcined composite ofa polyphosphoric acid and a siliceous adsorbent which comprises treatingsaid composite with a hydrolyzable salt of zirconium.

An additional embodiment of this invention elates to a process forimproving the structural strength of a calcined composite of apolyphosphoric acid and a siliceous adsorbent which comprises treatingsaid composite with hydrolyzable salt of tin,

13 Claims. (Cl. 252-435) A still additional embodiment of this inventionrelates to a process for improving the structural strength and activityof a calcined composite of a polyphosphoric acid and diatomaceous earthwhich comprises treating said composite with stannic chloride.

The essential and active ingredient of the solid catalysts which aremanufactured by the present process for use in organic reactions is anacid of phosphorus, preferably one in which the phosphorus has a valenceof 5. The acid may constitute to about or more of the catalyst mixtureultimately produced, and in most cases, is over 50%. byweight thereof.Of the various acids of phosphorus, orthophosphoric acid (H3PO4) andpyrophosphoric acid (H4P2O'z) find general application in the primarymixtures, due mainly to their cheapness and to the readiness with whichthey may be procured although the invention is not restricted to theiruse but may employ any of the other acids of phosphorus insofar as theyare adaptable. It is not intended to infer, however, that the differentacids of phosphorus, which may be employed will produce catalysts whichhave identical effects upon any given organic reaction as each of thecatalysts produced from difierent acids and by slightly varied procedurewill exert its own characteristic action.

When orthophosphoric acid is used as a primary ingredient, difierentconcentrations of the aqueous solution may be employed fromapproximately 75 to or acid containing some free phosphorus pentoxidemay even be used. By this is meant that the ortho acid may contain adefinite percentage of the pyro acid corresponding to the primary phaseof dehydration of the ortho-phosphoric acid. Within these concentrationranges, the acids will be liquids of varying viscosities, and readilymixed with adsorbent materials. In practice it has been found thatpyrophosphoric acid corresponding to the formula H4P2O7 can beincorporated with siliceous adsorbents at temperatures somewhat aboveits melting point (142 F.) and that the period of heating which is givento the pyro acid-adsorbent mixtures or to mixtures of otherpolyphospho-ric acids and siliceous adsorbents may be different fromthat used when the ortho acid is so employed.

Triphosphoric acid which may be represented by the formula HsPsOio mayalso be used as a starting material for preparation of the catalysts ofthis invention. These catalytic compositions may also be prepared fromthe siliceous materials morillonite, acid-treated mentioned herein and aphosphoric acid mixture containing orthophosphoric, pyrophosphoric,triphosphoric, and other polyphosphoric acids.

Another acid of phosphorus which may be employed in the manufacture ofcomposite catalysts aocording-tothe present invention is tetraphosphoricacid. It has the general formula H6P40l3 which corresponds to the doubleoxide formula 31-120. 21205 which in turn may be considered as the acidresulting when three molecules of Water are lost by four moleculesoforthophosphoric acid HsPOi. The tetraphosphoric acid may be manufacturedby the gradual and controlled dehydration by heating :of orthophosphoricacid or pyrophosphoric acid or by adding phosphorus pentoxide to theseacids in proper amounts. When the latter procedure is followed,phosporic anhydride is added gradually until it amounts to 520% byweight of the total water present. After a considerable period ofstandingat crdinary temperatures, the crystals'of the .tetraphosphoricacid separate from the viscous .liquidand it is found that thesecrystals melt at approximately 93 F. and have a specific gravity :of1.1866 at a temperature of 60" F. However, it is unnecessary tocrystalize the tetraphosphorio :acid before employing it in thepreparation of :thesolid :catalysts inasmuch as the crudetetraphosphoric acid mixture may be incorporated with the siliceous:adsorbent and other catalyst -ingredient.

The materials which may be employed as ad- ;sorbents or-carriers ,foracids of phosphorus in- ,cludesiliceOus:adsorbents such as diatomaceousearth, kieselguhr, artificially prepared silica, and also certainaluminum silicates which include .such naturally occurring substances asvarious ,fullers earths, clays, such as bentonite, montclays, alsorefractory oxides, as alumina, magnesia, etc., carbon, and similarmaterials. Each adsorbent or supporting material which may .be used willexert its .own

specific influence .upon the final catalyst composite formed in .theprocess.

Hydrolyzable compounds and particularly readily hydrolyzablesalts oftitanium, zirconium, and tin .are useful for treating precalcinedcomposites of a phosphoric acid and .a carrier to improve the structuralstrength and catalytic activity of said composite. ,Suohhydrolyzablesalts of titanium, zirconium, and tin, include the halides, oxyhalides,nitrates, sulfates, and salts of organic acids. The halides includefluorides, chlorides, bromides and iodides. Some of thesediiierentihvdrolyzable c. zirconium. and tin are either readily volatileat temperatures below about 350 .C. or they have appreciable solubilityin solvents including organic solvents such as saturated hydrocarbons,alkyl ethers, esters, alcohols, and also in water which maybe regardedas an inorganic solvent. Examples .of such 'hydrolyzable compounds aretitanium tetrachloride, zirconium tetrachloride, and tin tetrachloride.

The treatment of a calcined composite of a phosphoric acid and a carrierwith one or more of the aforementioned hydrolyzable compounds maybecarried out by one of the following methods.

-(1) The calcined composites may be maintained at a temperature of fromabout 100 to about 550" C. and contacted with vapors of said volatilecompound or with a mixture of vapors of said volatile compound and acarrier gas such as nitrogen, helium, etc., which has no adversereaction with the volatile compo nd.

ompounds of titanium, I

phosphate and thus increasing the strength of the treated catalyst.

solid material.

The treated composite may carrier, particularly, a siliceous carrier,

posite of a phosphoric acid and a carrier with a hydrolyzable compoundof titanium, zirconium, or tin, the amount of said hydrolyzable compoundis controlled so that the resultant treated phosphoric acid-containingcatalyst will contain from about 1 to about 10% by weight of a phosphateof said titanium, zirconium, or tin so added in the form of thehydrolyzable compound to the solid cdtalyst forming a metal structuralComposites .of a phosphoric acid and a carrier are prepared by mixingthe phosphoric acid with the finely-divided relatively inert carriergenerally at a temperature of from about 20 to about 250 .C. to formanaggregate in which the phosphoric acid is ordinarily the majorproportion by weight. The resultant aggregate is a slightly moist toalmost dryzmaterial which upon being compressed becomes sufficientlyplastic so that it can be extruded and formed into shaped particles. Theresultant particles are then dried and calcined at .a temperature offrom about 160 to about 550 C. for a time of from about 0.25 to about1.0 hours .to form a substantially The calcining operation may becarried out .byheating the formed particles in a substantially inert gassuch as air, nitrogen, flue gas and the like. These calcined particlesare then composited with a hydrolyzable salt of titanium, zirconium, ortin as herein set forth.

Acalcined composite of ,an acid of phosphorus and a carrier,particularly a siliceous carrier such as diatomaceous earth, is treated,for example, Withstannic chloride vapors or with a mixture of vapors ofstannic chloride and a substantially saturated hydrocarbon solvent.Alternatively, the particles of the calcined composite may be mixed withor soaked, for example, in a solution of stannic chloride dissolved in asuitable solvent. then be separated from the excess of the treatingsolution by decanting or distilling said solution or solvent therefrom.after which the catalyst particles wetted with the solution ofstannicchloride are heated in an inert atmosphere to remove excesssolvent and also the remainder of the volatile tin compound to form asolid catalytic material with catalytic activity and structural strengthgreater than those of the calcined composite of a phosphoric acid and acarrier which was subjected to this treating step with stannic chloridein a hydrocarbon solvent.

Calcined composites of a phosphoric acid and a which have been treatedas herein set forth, with, for example, stannic chloride, titaniumchloride or zirconium chloride, are active for promoting polymerizationof olefinic hydrocarbons, particularly for promoting polymerization ofnormally gaseousolefinic hydrocarbons to form normally liquidhydrocarbons suitable for use "as constituents of gasoline. Whenemployed in the conversion of olefinic hydrocarbons into polymers, thecalcined catalyst formed as herein set forth, is preferably employed asa granular layer in a heated reactor, which is generally made fromsteel, and through which the preheated hydrocarbon fraction is directed.Thus the solid catalyst of this process may be employed for treatingmixtures of olefincontaining hydrocarbon vapors to effect olefinpolymerization, but this same catalyst may also be used at operatingconditions, suitable for maintaining liquid phase operation duringpolymerization of olefinic hydrocarbons, such as butylenes, to producegasoline fractions. Thus when employed in the polymerization of normallygaseous olefins, the formed and calcined catalyst particles aregenerally placed in a vertical, cylindrical treating tower and theolefin-containing gas mixture is passed downwardly therethrough at atemperature of from about 350 to about 550 F. and at a pressure of 100to about 1500 pounds per square inch when dealing with olefin-containingmaterials such as stabilizer reflux which may contain from approximatelyto 50% or more of propylene and butylene. When operating on a mixturecomprising essentially butanes and butylenes, this catalyst is effectiveat conditions favoring the maximum utilization of both normal butylenesand isobutylene which involves mixed polymerization at temperatures offrom approximately 250 to about 325 F. and at pressures of from about500 to about 1500 pounds per square inch.

When the catalysts of this invention are utilized for promotingmiscellaneous organic reactions, the catalysts may be employed inessen-' tially the same way as they are used when polymerizing olefins,in case the reactions are essentially vapor phase, and they also may beemployed in suspension in liquid phase in various types of equipment.

With suitable modifications in the details of operation, the presenttype of catalyst may be employed in a large number of organic reactionsincluding polymerization of olefins as already mentioned. Typical casesof reaction in which the present type of catalyst may be used are thealkylation of cyclic compounds with olefins, the cyclic compoundsincluding aromatics, polycyclic compounds, naphthenes, and phenols;condensation reactions such as those occurring between ethers andaromatics, alcohols and aromatics, phenols and aldehydes, etc.,reactions involving the hydro-halogenation of unsaturated organiccompounds, isomerization reactions, ester formation by the interactionof carboxylic acids and olefins, and the like. The specific procedure ofutilizing the present type of catalysts in miscellaneous organicreactions will be determined by the chemical and physicalcharacteristics and the phase of the reacting constituents.

During use of these catalysts in vapor phase polymerizations and othervapor phase treatments of organic compounds, it is often advisable toadd small amounts of moisture to prevent excessive dehydration andsubsequent decrease in catalyst activities. In order to substantiallyprevent loss of water from the catalyst an amount of Water or watervaporsuch as steam is added to the charged olefin-containing gas so asto substantially balance the vapor pressure of the catalyst. This amountof water vapor varies from about 0.1 to about 6% by volume of theorganic material charged.

Solid phosphoric acid catalysts which have been prepared heretofore bycalcining composites of a siliceous adsorbent and a phosphoric acidfrequently lose much of their activities during polymerization use andalso suffer marked decrease in crushing strength due to the softening ofthe catalyst. Such softening of the catalyst also results in shortcatalyst life inasmuch as the catalyst towers become plugged during use.In this process, I have found that catalysts of high crushing strengthmay be produced by adding a hydrolyzable tin to a composite ofphosphoric acid and diatomaceous earth in which an amount of from about1 to about 10% by weight (based upon the weight of total catalyst) ofmetal phosphate is formed in the final catalyst composite.- Such acatalyst composite which has been treated with a tetrachloride oftitanium, zirconium, or tin or with another readily hydrolyzable salt ofsuch metals also has a good crushing strength after it has been used inpolymerization of propylene or in the polymerization of other olefinichydrocarbons.

The following examples illustrate the preparation of catalysts comprisedwithin the scope of the invention and give results obtained in their usefor catalyzing the polymerization of propylene, although the exactdetails set forth herein are not to be construed as imposing unduelimitations upon the generally broad scope of the invention.

EXAMPLE I Table I shows results obtained in an autoclave polymerizationtest on a catalyst prepared from phosphoric acid and diatomaceous earthwhich had been treated with 2% by weight of stannic chloride in pentanesolution by the method described herein. The catalyst activity test wascarried out by placing 10 grams of 5 x 5 mm. pellets of catalyst andgrams of a propanepropylene mixture (53.3% propylene content) in arotatable steel autoclave of 850 cc. capacity which was then rotated ata temperature of 450 F. for 2 hours. At the end of this time,determination was made to indicate the percentage conversion ofpropylene into liquid polymers.

TABLE I Propylene polymerizing activities and crushing strengths ofcatalysts formed by treating a calcined composite polyphosphorzc acidand diatomaceous earth with stannic chloride Crushing An unexpectedenhancement in activity was 1 observed in the case of th catalysttreated with stannic chloride and later calcined at a tempera-- ture of680 F. This particularly treated catalyst promoted polymerization of81.8% of the propylene charged to the autoclave on comparison with 66.5%propylene polymerization effected in the presence of the originalcalcined composite of polyphosphoric acid and diatomaceous earth towhich no stannic chloride has been added (run 2).

Also the after-use crushing strength of 10.2 pounds was better than thecorresponding value of 5.4 pounds found in the case of the originalcatalyst which was not treated with stannic chloride.

salt of titanium, zirconium, or-

7 EXAMPLE 11 v V A calcined composite of polyphosphoric acid anddiatomaceous earth like that referred to in Example I was also treatedwith aqueous solutions of zirconium tetrachloride as indicatedhereinafter. Extruded x 5 mm. pellets of solid phosphoric acid catalystswere treated with an aqueous solution containing by weight of zirconiumtetrachloride. These catalysts were prepared by soaking 54 grams of thesolid phosphoric acid pellets with 5.9 grams of a solution produced bydissolving 2.7 grams of zirconium tetrachloride in 25 cc. of water. Thewet pellets were dried for one hour at a temperature of 500 F. anddivided into two portions; one portion of the treated pellets wascalcined for one hour at a temperature of 680 F. and the other portionof the dried pellets was calcined for one hour at a temperature of 860F. 7

Some of the commercially prepared solid phosphoric acid pellets werealso treated with an aqueous solution contai mg 28% by weight orzirconium tetrachloride. In this treatment 54 grams of the solidphosphoric acid pellets were soaked with 11.4 grams of a solutionprepared by dissolving 10.4 grams of zirconium tetrachloride in 28 cc.of water. The wet pellets were dried first at 500 F. for one hour andthen one-hair oi the pellets was calcined for one hour at 680 F. and theother one-half was calcined for one hour at a temperature of 860 F.

Table II shows comparative results obtained in autoclave polymerizationtests on these catalysts using propane-propylene mixture as the test gasby the procedure referred to in Example I.

TABLE II the group consisting of titanium, zirconium; and tin in anamount suflicient to add from about 1 to about 10% by weight of aphosphate of said metal to said calcined composite, and furthercalcining the resultant composite to form a solid catalytic material ofgreater structural strength than that of the original calcined compositeof phosphoric acid and solid supporting material.

2. A process for improving the structural strength of a calcinedcomposite of an acid of phosphorus and a siliceous carrier whichcomprises treating said composite with a hydrolyzable compound of ametal selected from the group consisting of titanium, zirconium, and tinin an amount sufficient to add from about 1 to about 10% by weight of aphosphate of said metal to said calcined composite, and furthercalcining the resultant composite to form a solid catalytic material ofgreater structural strength than that of the original calcined compositeof phosphoric acid and a siliceous carrier.

3. A process for improving the structural strength of a calcinedcomposite of a polyphos" phoric acid and. diatomaceous earth whichcomprises treating said composite with titanium tetrachloride in anamount suflicient to add from about 1 to about 10% by weight of titaniumphosphate to said calcined composite, and further calcining theresultant composite at a temperature of from about 100 to about 550 C.to form a solid catalytic material of greater structural strength thanthat of the original calcined composite of polyphosphoric acid anddiatomaceous earth.

4. A process 'for improving the structural Propylene polymerizingactivities and crushing strengths of catalysts formed by treating acalcined composite of polyphoric acid and oliatomaceoas earth withzirconium tetrachloride solution 232 C. in a rotating autoclave of 850cc. capacity] Materials added to l From Table II it is noted that thetreatment of solid phosphoric acid catalyst pellets with an aqueoussolution of zirconium tetrachloride improved the crushing strengths ofthe three catalyst samples so treated. Thus the after-use crushingstrength of the zirconium tetrachloride treated catalysts was from 13.6to 19.9 pounds in comparison with a value of 5.4 pounds found in thecase of the original solid phosphoric acid catalysts which had not beentreated with zirconium tetrachloride solution.

I claim as my invention:

1. A process for improving the structural strength of a calcinedcomposite of an acid of phosphorus and a solid supporting material whichcomprises treating said composite with a hydrolyzable compound of ametal selected from Crushing calcined composite oalcmatlon Percentstrength, lbs. Run of polyphosphoric ABD, Oonv. No. acid anddiatomag./cc. Propylceous earth F. Hours ene Before After Use Use 3Zirconium tetraohlo- 680 1 0 836 53 2 16. 5 l7. 5

ride (10% solution). A 4 o 860 l 0 837 61 8 l4. 8 13. 6 5 Zirconiumtetrachlo- 680 l 0 757 67 0 20. 6 l9. 9

ride (28% solution). 2 None 66 5 11.4 5.4

1 Apparent bulk density. 2 53.3% propylene in test gas.

strength of a calcined composite of a polyphosphoric acid anddiatomaceous earth which comprises treating said composite withzirconium tetrachloride in an amount sufiicient to add from form a solidcatalytic material of greater structural strength than that of theoriginal calcined composite of polyphosphoric acid and diatomaceousearth.

5. A process for improving the structural strength of a calcinedcomposite of polyphosphoric acid and diatomaceous earth which comprisestreating said composite with tin tetrachloride in an amount sufficientto add from about 1 to about 10% by Weight of tin phosphate to saidcalcined composite, and further calcining the resultant composite at atemperature of from about 100 to about 550 C. to form a solid catalyticmaterial of greater structural strength than that of the originalcalcined co5mposite of polyphosphoric acid and diatomaceous earth.

6. A process for improving the structural strength of a calcinedcomposite of pyrophosphoric acid and diatomaceous earth which comprisestreating said composite with titanium tetrachloride in an amountsufiicient to add from about 1 to about 10% by weight of titaniumphosphate to said calcined composite, and further calcining theresultant composite at a term perature of from about 100 to about 550 C.to form a solid catalytic material of greater structural strength thanthat of the original calcined composite of pyrophosphoric acid anddiatomaceous earth.

'7. A process for improving the structural strength of a calcinedcomposite of pyrophosphoric acid and diatomaceous earth which comprisestreating said composite with zirconium tetrachloride in an amountsufficient to acid from about 1 to about 10% phosphate to said calcinedcomposite, and rurther calcining the resulant composite at aternperature of from about 100 to about 550 C. to form a solid catalyticmaterial of greater structural strength than that of the originalcalcined composite or pyrophosphoric acid and cliatomaceous earth.

8. A process for improving the structural strength of a calcinedcomposite of pyrophosphoric acid and diatomaceous earth which comprisestreating said composite with tin tetra chloride in an amount suflicientto add from about 1 to about 10% by weight of tin phosphate to saidcalcined composite, and further calcining the resultant composite at atemperature of from about 100 to about 550 C. to form a solid catalyticmaterial of greater structural strength than that of the originalcalcined composite of pyrophosphoric acid and diatomaceous earth.

9. A process for improving the structural strength of a calcinedcomposite of pyrophosphoric acid and diatomaceous earth which comprisestreating said composite with titanium tetrachloride in an amountsuihcient to add from 1 to about about 10% by weight of titaniumphosphate to said calcined composite, and further calcining theresultant composite at a temperature of from about 100 to about 550 C.for

l a time of from about 0.25 to about 10 hours to form a solid catalyticmaterial of greater strucby weight of zirconium 1 tural strength thanthat of the original calcined composite of pyrophosphoric acid anddiatomaceous earth.

10. A process for improving the structural strength of a calcinedcomposite of pyrophosphoric acid and diamtomaceous earth which comprisestreating said composite with zirconium tetrachloride in an amountsufficient to add from about 1 to about 10% by weight of zirconiumphosphate to said calcined composite, and further calcining theresultant composite at a temperature of from about 100 to about 550 C.for a time of from about 0.25 to about 10 hours to form a solidcatalytic material of greater 11. A process for improving the structuralstrength of a calcined composite of pyrophosphoric acid and diatomaoeousearth which comprises treating said composite with tin tetrachloride inan amount suflicient to add from about 1 to about 10% by weight of tinphosphate to said calcined composite, and further calcining theresultant composite at a temperature of from about 100 to about 550 C.for a time Of from about 0. 5 to about 10 hours to form a solidcatalytic material of greater structural strength than that of theoriginal calcined composite of pyrophosphoric acid and diatomaceousearth.

12. A solid catalytic material formed by treat ing a precaloinedcomposite of polyphosphori acid and diatomaceous earth with an amount oftin tetrachloride sufiicient to add from about 1 to about 10% by Weightof tin phosphate to said precalcined composite and further calcining theresultant composite at a temperature of from about 100 C. to about 550C. for a time of from about 0.25 to about 10 hours.

13. A solid catalytic material formed by treating a precalcinedcomposite of a phosphoric acid and in an amount sumcient to add fromabout 1 to about 10% by weight of tin phosphate to said composite andcalcining the resultant mixture at a temperature of from about 100 C. toabout 550 C. for a time of from about 0.25 to about 10 hours.

JULIAN M. MAVITY.

References Cited in the file of this patent UNITED STATES PATENTS

1. A PROCESS FOR IMPROVING THE STRUCTURAL STRENGTH OF A CALCINEDCOMPOSITE OF AN ACID OF PHOSPHORUS AND A SOLID SUPPORTING MATERIAL WHICHCOMPRISES TREATING SAID COMPOSITE WITH A HYDROLYZABLE COMPOUND OF AMETAL SELECTED FROM THE GROUP CONSISTING OF TITANIUM, ZIRCONIUM, AND TININ AN AMOUNT SUFFICIENT TO ADD FROM ABOUT 1 TO ABOUT 10% BY WEIGHT OF APHOSPHATE OF SAID METAL TO SAID CALCINED COMPOSITE, AND FURTHERCALCINING THE RESULTANT COMPOSITE TO FORM A SOLID CATALYTIC MATERIAL OFGREATER STRUCTURAL STRENGTH THAN THAT OF THE ORIGINAL CALCINED COMPOSITEOF PHOSPHORIC ACID AND SOLID SUPPORTING MATERIAL.